i have never heard about the framework before and just took a look at the examples.
the theming is nice, but the coding style reminds me a lot on jQuery: they add script tags inside the dom to render components there and use the $ syntax.

so, my first impression is, that is a nice collection of widgets, but not a real framework to build pure JS apps.

reminds me of the slick grid. even a step better than my tobiuGrid: i went down the road minifying css.
this grid is almost a pure html table: each second tr tag has one class for alternate rowcolor, the td tags have no class applied at all, there are no divs with classes inside the tds.

this markup will limit complex features but for a basic version perfect.

I remember reading about it when our Telerik license expired (happily, I might add!) and thought it looked nice, but it's targeted at people who still want to write HTML tags and do the CSS layout themselves. Ext JS is a very different beast and is targeted at developers who want to write a GUI more like a Java app, with layout managers, etc. If I was still using jQuery and manually creating separate HTML files for each page view, I'm sure Kendo UI would be good, but I don't think I'd ever go back to touching HTML/CSS, certainly not after using Ext JS.

Yes, I've used it before. The thing I liked about it was the MVVM and declarative data-binding features. The UI components are pretty nice and it looks great out of the box. As others stated, it's built with jQuery, so if you're looking to take a jQuery approach to the next level, it's pretty good. I didn't have great luck when trying to build a single page app, though they do have examples of doing so. I also had difficulty in trying to build re-usable components. It seems to be better suited for multiple page apps, as it doesn't really have much in terms of dependency management or view management (except for the touch version). But the view model approach works well and can help to put better organization to apps on the smaller, less complicated side.

I'm a huge fan of data-binding and the MVVM/Presentation Model pattern, all the way back from the days of Flex. When I was using Ext 4.x, I always felt like I didn't like the Sencha MVC implementation. I actually started to drift away from Ext JS towards other frameworks like Angular, Knockout, KendoUI, which were adopting MVVM. But those frameworks lack so much of what Ext JS brings to the table - basic things like dependency management, solid architectural patterns, classic OOP, and great UI components including charts. Now that Ext JS 5 has gone the way of MVVM, I am back in love with Sencha. I really don't think the others can compare. Just my 2 cents...

I tried Sencha MVC in my previous project, and hated it. With my current project (of the past five months, nearing completion) I went back to just wiring up events to buttons/grids/etc directly to each component in Sencha Architect. I don't have time to constantly switch back and forth between controller and view for things that are often single-use. Even if they are multiple-use, wiring events on the view hasn't caused me any grief yet.

Finding the right syntax to wire up handlers in the controller was always too time consuming, and it was always difficult to determine things about the current instance of a view controller.

I'll give MVVM a go in Ext JS 5 for my next project. Hopefully it's better. I'm also hoping for Sencha Architect improvements, like a shortcut key to comment/uncomment a block of code. Currently there are too many impediments to adopting best practise with everything on a day-to-day basis. If something is best practise but takes too long to type and setup by comparison, I ain't doing it, basically.